The present disclosure relates to medical devices and procedures. In particular, it relates to hemostatic valves and systems, and methods of using the same.
Numerous procedures have been developed that involve the percutaneous insertion of a medical device into a body vessel of a patient's body. Such a device may be introduced into the vessel by a variety of known techniques. For example, a wire guide may be introduced into a vessel using the Seldinger technique. This technique involves creating a surgical opening in a vessel with a needle and inserting a wire guide into the vessel through a bore of the needle. The needle can be withdrawn, leaving the wire guide in place. An introducer device is then inserted over the wire guide and into the vessel. The introducer device may be used in conventional fashion to insert into the body vessel a variety of medical devices, such as catheters, cardiac leads, balloons, stents, stent grafts, and the like.
For example, an introducer device may be used to deliver and deploy an endoluminal prosthesis, such as a stent or stent graft, to treat a damaged or diseased body lumen such as a bile duct or a blood vessel. The deployment of the endoluminal prosthesis into the lumen of a patient from a remote location by the use of an introducer delivery and deployment device is well known in the art. For example, U.S. Pat. No. 7,435,253 entitled “A Prosthesis and a Method and Means of Deploying a Prosthesis,” which is incorporated herein by reference in its entirety, proposes a delivery and deployment system for an endoluminal prosthesis. The prosthesis is radially compressed onto a delivery catheter and is covered by an outer sheath. To deploy the system, the operator slides the outer sheath over the delivery catheter, thereby exposing the prosthesis for outward expansion thereof.
One of the challenges associated with endoluminal procedures is controlling the flow of bodily fluids within the introducer device during the procedure. Valve devices may be provided when it is necessary or desired to control fluid flow. For example, the introducer device may include a hemostatic valve to limit or prevent blood loss through the introducer device during a procedure. Various hemostatic valve devices have been described in the patent literature. U.S. Pat. App. Publ. No. 2007/0078395 A1, which is incorporated herein by reference in its entirety, for example, discloses numerous examples of hemostatic valve devices and systems that use disk valves to control fluid flow.
Another type of hemostatic valve device that is presently in use for sealing elongated passages in a medical device to prevent loss of blood is known as an iris valve. An iris valve is described in U.S. Pat. No. 5,158,553, which is incorporated herein by reference in its entirety. The valve described in the '553 patent comprises a valve hub that is joined to a catheter-type device, and a rotatable cap that is joined to the hub. An elastomeric sleeve is positioned in an opening through the interior of the valve body. Each end of the elastomeric sleeve is joined to the rotatable cap by wrapping and clamping the respective end around a clamping mechanism. When the cap is rotated in a first direction, the circular opening of the elastomeric sleeve is fully opened. When the cap is rotated in a second direction opposite the first direction, the elastomeric sleeve is twisted intermediate the two ends to effect closure of the circular opening. Due to the elastomeric properties of the sleeve, the circular opening of the elastomeric sleeve constricts as the cap is rotated to effect closure.
Although the valve of the '553 patent is generally effective for sealing sheaths of certain sizes and compositions, the general design of the valve assembly of the '553 patent has certain shortcomings. For example, the manner of engaging the ends of the seal to the respective hub and cap is less than optimal. Such ends are capable of disengagement, which destroys the ability of the valve to form a seal. In addition, the seal does not include provisions to prevent recoil of the seal after rotation of the rotatable cap to position the seal in a desired position. As a result, if the operator relaxes the rotational pressure on the valve, the seal can revert, or recoil, to its original (unsealed) position. Yet another problem with the iris valve assembly as described in the '553 patent is that longitudinally extending gaps or channels are capable of being formed along the seal, which gaps or channels can extend through the valve after rotation of the valve to the closed position. When such gaps or channels are present, fluid can leak through them in the valve seal. Furthermore, the configuration of such valves renders them subject to tearing. As shown in FIG. 5 of the '553 patent, only a small portion of the entire iris valve assembly forms the seal along the sheath, e.g., less than about 20% of the length of the elastomeric sleeve.
Often, a single introducer device may be used to insert multiple medical devices during a single procedure. For example, a single introducer sheath with a hemostatic valve device may be used first for introducing a delivery catheter for deployment of an endoluminal prosthesis within a vessel. Once the prosthesis is placed within the vessel, the single introducer sheath with the hemostatic valve device is also used to deliver an interventional catheter, such as a balloon catheter, to the vessel to cause expansion of the deployed prosthesis. In this example, the hemostatic valve device must be able to provide a hemostatic seal under at least three distinct conditions: 1) to seal against the delivery catheter carrying the endoluminal prosthesis when inserted in the introducer sheath and valve device; 2) to seal when the delivery catheter is removed from the introducer sheath and valve device; and 3) to seal against the interventional catheter when inserted in the introducer sheath and valve device.
One problem with using a single introducer device for multiple medical devices is that each medical device can have a different diameter. Thus, the ideal hemostatic valve device will be able to accommodate and seal over a wide range of diameters of the medical devices. For example, it may be advantageous for a hemostatic valve device to seal well around the surface of a delivery catheter, as well as a wire guide that is 50%, 25%, 10%, or smaller in diameter relative to the diameter of the delivery catheter, or to seal even when there is no device present. Moreover, such a hemostatic valve device should be able to adjust quickly to large variations in diameter.